<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    .container {
      width: 222px;
      height: 294px;
      border-radius: 50%;
      overflow: hidden;
    }

    .container img {
      opacity: .4;
    }
  </style>
</head>

<body>
  <script>
    /*
      1.透明
      - 颜色透明，但元素仍旧存在
    */
  </script>
  <div class="container">
    <img src="imgs/img_01.png" alt="">
  </div>
</body>

</html>